Reinforcing movable head for protection against ruptured cartridge cases

ABSTRACT

In order to improve the obturation capability of firearm cartridges fabricated from materials other than brass, the usual enlarged extraction rim at the rear end thereof is replaced by a ring fabricated from a more deformable material than the case and provided with a beveled forward portion arranged to be expanded into obturating contact with the interior of the firing chamber in response to the forward movement of the bolt into battery position. The ring also includes an exterior groove engageable with the extractor carried by the bolt and an interior groove into which the firing pressures will swage the material of the cartridge case to provide sufficient locking engagement therebetween to withstand the extraction forces imparted thereto by the extractor during the recoil travel of the bolt.

United States Patent 1 1 3,771,452 Reed et al. Nov. 13, 1973 i 1REINFORCING MOVABLE HEAD FOR FOR I NP EN S R PPLC TI NS PROTECTIONAGAINST RUPTURED E G AT T O A I A O CARTRIDGE CASES 213,678 9/1909Germany 102/44 [75] Inventors: Frederick P. Reed, Davenport, Iowa;Primary Examiner-Robert F. Stahl J. Phillip Langdon, Moline, Ill.Attorney-Harry M. Saragovitz et :al. [73] Assignee: The United States ofAmerica as represented by the Secretary of the t [57] ABSTRACT Army,Washington, DC. In order to improve the obturatioln capability of firevarm cartridges fabricated from materials other than [22] Flled' 1972brass, the usual enlarged extraction rim at the rear end [2]] Appl. No.:242,057 thereof is replaced by a ring fabricated from a more deformablematerial than the case and provided with a beveled forward portionarranged to be expanded into 02/43 421; obturating contact with theinterior of the firing cham- [58] Fie'ld 40 43 R ber in response to theforward movement of the bolt into battery position. The ring alsoincludes an exte- 102/43 89/26 rior groove engageable with the extractorcarried by [56] References Cited the bolt and an interior groove intowhlch the firing pressures Will swage the material of the cartridge caseUNITED STATES PATENTS to provide sufficient locking engagement therebe-3,690,256 9/1972 Schnitzer 102/44 tween to withstand the extractionforces imparted 2,654,319 10/953 Roske 102#13 P thereto by the extractorduring the recoil travel of the 3,026,802 3/1962 Barnet et al. 102/44 xbolt 3,675,576 7/1972 Whitney .r 102/44 2,823,611 2/1958 Thayer 102/44 4Claims, 4 Drawing Figures REINFORCING MOVABLE HEAD FOR PROTECTIONAGAINST RUPTURED CARTRIDGE CASES BACKGROUND OF THE INVENTION Thisinvention relates to firearm cartridges fabricated from materials ofless deforrnability than brass and is more particularly directed tomeans for improving the obturation between the cartridge case and thefiring chamber to prevent rearward escape of the gases generated duringfiring especially in the event of a rupture, break, or leak in the case.

While the case portions of military firearm cartridges are usuallyfabricated of brass in order to provide the strength and deforrnabilityrequired to insure rapid obturation of the firing chamber in the firearmagainst the rearwardescape of the discharge gases, the increasingscarcity and cost of copper has prompted numerous attempts to utilizemolded organic plastics, aluminum, or even steel as a substitutematerial. These attempts have met with some degree of success infirearms designed for commercial and sporting use but have not beenacceptable where the cartridges have been of the high pressure typerequired for military firearms which are operated at high rates ofsustained fire. The major drawback of these lighter and less costlymaterials has been their inability to expand with sufficient rapidityinto full obturating contact with the interior of the firing chamber inthe firearm. Furthermore, where the need for a substantial reduction inthe weight of the cartridges has dictated the fabrication of the caseportions thereof from a lightweight material such as aluminum, it hasbeen found that the feeding of a belt of linked cartridges into thefirearm and the subsequent delinking of each cartridge prior to thechambering thereof frequently produces nicks and scratches thereon ofconsiderable depth relative to the wall thickness of the case itself. Inview of the relatively thin walls required of aluminum cases in order tomaximize the rapidity of the obturating expansion thereof in response tothe firing pressures, any imperfections or reductions reaches the wallthickness introduces the possibility of actual ruptures or breaks priorto the completion of firing. Obviously, any failure to fully obturatethe firing chamber against the extremely hot and corrosive gasesgenerated during firing could lead to catastrophic fail ure of thefirearm as well as severe injury to the operator thereof.

SUMMARY OF THE INVENTION It has been found that the foregoingdifficulties can be eliminated by modifying a conventional cartridgecase of aluminum or other lightweight material to omit the annularflange customarily utilized to form the rear wall of the extractorgroove and utilizing the remaining cylindrical portion to seat anobturating ring of a more deformable material than that employed in thecase. The forward end of such ring is interiorly beveled at a steeperangle than the inclined annular shoulder extending forwardly from thecylindrical rear end portion of the cartridge case. Thus, as the firearmbolt is advanced into position to close the breech, it forces the ringforwardly causing the beveled portion thereof to ride up the annularshoulder on the cartridge case and be diametrically expanded intoobturating contact with the interior surface of the firing chamber. Thisinitial expansion of the ring is thereafter increased by the setbackimparted to the cartridge case during firing to more effectively sealthe gap ordinarily left between the front face of the firearm bolt andthe rear face of the barrel after the former reacher battery position.

The obturating ring is also provided with an extracter groove in theexterior periphery thereof to permit the customary withdrawal of thefired cartridge case from the firearm barrel during the opening of thebreech. In order to prevent separation between the obturating ring andthe cylindrical rear end portion of the fired cartridge case duringextraction, the interior of the ring is formed with a shallow annulargroove arranged to receive the metal which is swaged or otherwise forcedtherein in response to the extremely high firing pressures exertedagainst the relatively thin cross-section surrounding the primer cavity.In addition to the locking. function thereof, the ring also sealsagainst the rearward leakage of any discharge gases in the event arupture or break in the cartridge case permits a hypervelocity gas flowbetween the inclined mating surfaces on the ring and on the shoulder ofthe case.

It is therefore an object of this invention to provide an improvedfirearm cartridge wherein the rear end of the case portion thereof isprovided with a separate obturating ring for sealing the firing chamberagainst the potential rearward escape of the discharge gases.

Another object of this invention; is to provide a cartridge case with anobturating ring which will be advanced into initial sealing contact withthe interior of the firing chamber in the firearm barrel during theclosure of the breech.

Still another object of the present invention resides in the provisionof a firearm cartridge, as aforesaid, which will fully obturate thefiring chamber therefor even in the event of a rupture or break in thewalls of the cartridge case prior to the completion of the firingexpansion thereof.

An additional object of this invention is to provide a obturating ring,as aforesaid, which will also serve to transfer the breech openingmovement of the firearm bolt to the fired cartridge case in order toeffect the extraction thereof from the firing chamber.

BRIEF DESCRIPTION OF THE DRAWING The exact nature of the invention, aswell as other objects and advantages thereof, will be readily apparentfrom consideration of the following specifications relating to theannexed drawing wherein:

FIG. 1 is a central longitudinal section of portions of a firearm breechand bolt and includes a cartridge provided with the obturating ring ofthe present invention, the parts being shown immediately prior to thecompletion of the forward travel of the bolt into battery position;

FIG. 2 is a view similar to that of FIG. 1 but showing the initialobturating position imparted to the ring at the conclusion of theclosure of the breech;

FIG. 3 is a view similar to that of FIGS. 1 and 2 but showing theposition of the obturating ring during the firing of the cartridge; and

FIG. 4 is a perspective view of the obturating ring partly broken awayto show the interior and exterior configuration thereof.

DESCRIPTION OF A PREFERRED EMBODIMENT As shown in the drawing, thepresent invention is particularly applicable to military cartridges I2of the type which are rammed into a firing chamber 14 in the breech endof a firearm barrel 16 by a forwardly moving bolt 18 provided with acartridge seating recess 20 in the front face thereof. While suchcartridges l2 customarily terminate in a flanged rim at the rear end ofthe case portion 22 which cooperates with an inclined annular shoulder24 spaced forwardly thereof to define an extractor groove, for thisinvention the rim is eliminated thereby leaving case portion 22 with acylindrical rear end 26 containing the cavity 28 required to house thecartridge primer 30. Although aluminum or an alloy thereof is preferablyselected as a substitute material for the standard brass, cartridges 12may also be fabricated from steel or a high strength molded organicplastic.

In order to improve the obturation of firing chamber 14 during thedischarge of cartridge 12, a ring 32 of a more deformable material thanthe material of the cartridge case 22 is press-fitted onto thecylindrical rear end 26 thereof into contact with annular shoulder 24thereon. Although not necessarily-limited thereto, ring 32 is preferablyfabricated of a hardened copper or of brass with a high copper contentto insure maximum deformability while still retaining some degree ofstrength for a purpose to be explained. The forward portion ofobturating ring 32 is interiorly beveled, as indicated at 34, to providea forwardly decreasing cross-section terminating in a circular knifeedge 36, The angle of bevel 34 is steeper than that of annular shoulder24 on cartridge case 22 and consequently leaves a space 38 therebetweenof triangular configuration as best shown in FIG. 1. The portion of ring32 extending rearwardly of bevel 34 is of uniform diameter and ofsufficient length to project beyond case 22 to an extent at leastequivalent to the dimension of the base of triangular space 38.

The press-fit between ring 32 and cylindrical end 26 of case 22 issufiiciently tight to prevent dislodgrnent of ring 32 by the forcesnormally encountered during the feeding of cartridges 12 into thefirearm and the subsequent delinking operation required to free eachcartridge for insertion into firing chamber 14. However, once theforward travel of cartridge 12 into firing chamber 14 is completed, thecontinued movement of bolt 18 into locked battery position forcesobturating ring 32 forwardly thereby causing beveled portion 34 to moveinto mating contact with annular shoulder 24. As a result, beveledportion 34 is diametrically expanded as best shown at 39 in FIG. 2, intoobturating contact with the interior wall surface of firing chamber 14along a distance depending on existing tolerances and the degree ofdeformability of ring 32. This initial obturation of firing chamber 15serves to momentarily delay the flow of any discharge gases around theexterior of cartridge case 22 until the firing pressures reach the levelrequired to complete the set-back normally encountered during thebeginning of the firing cycle.

Once such set-back of cartridge case 12 is completed, the extent of theobturating contact between ring 32 and the interior surface of firingchamber 14 will be appreciably increased, as best shown in FIG. 3,thereby insuring positive sealing of the gap 40 ordinarily presentbetween the rear face of barrel 16 and the front face of bolt 18especially after the firing setback of cartridge 12 has been completed.Thus, even if cartridge case 22 should rupture or break prior tocompletion of the firing expansion thereof in firing chamber 14, therequired obturation thereof will be effectively accomplished by ring 32.Inasmuch as ring 32 and case 22 are fabricated of different materials,the propagation of any cracks or ruptures in the latter will beeffectively halted at the mating surfaces therebetween.

In order to provide for the subsequent extraction of the fired cartridgecase 22 during the recoil movement of bolt 18, an extractor groove 42 ofconventional configuration is provided in the exterior periphery ofobturating ring 32. In addition, the interior periphery of ring 32includes a relatively shallow groove 44 preferably in vertical alignmentwith extractor groove 42. As cartridge 12 is fired, the rising pressuretherein acts on the walls of primer cavity 28 to actually swage thematerial thereof into groove 44 in the interior wall surface ofobturating ring 32 as indicated at 46 in FIG. 3 thereby effectivelylocking such ring to cartridge case 22. Thus, ring 32 provides thegroove 42 required to receive the forward end of an extractor (notshown) on bolt 18 so that the recoil travel thereof will effect thewithdrawal of the fired case 22 from firing chamber 14 in barrel 16.

In addition to the locking function thereof, the material swaged intogroove 44 of obturating ring 32 also serves to seal against the flow ofany of the discharge gases between the inclined mating surfaces ofannular shoulder 24 and beveled portion 34 which has been found to takeplace in the event of any rupture or break in case 22 prior tocompletion of the firing expansion thereof in firing chamber 14.

Thus, there is here provided a simple yet positive means for effectivelyobturating the firing chamber against the rearward escape of thedischarge gases ordinarily encountered during the firing of an aluminumcartridge therein in the event the case thereof cracks or ruptures priorto completion of the firing expansion thereof.

We wish it to be understood that we do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

We claim:

1 A cartridge for a firearm having a barrel cooperating with areciprocal bolt in the battery position thereof to complete a splitfiring chamber, said cartridge comprising,

a case having a rearwardly facing beveled shoulder and a cylindricalportion of reduced diameter extending rearwardly from said shoulder, and

an obturating ring of a more deformable material than said case seatedon said cylindrical portion and having a beveled front end concentricwith said beveled shoulder and sloped to form a triangular spacetherebetween, said ring being equal in diameter to said case and ofsufficient length to project rearwardly beyond said cylindrical portioninto the path of the bolt during the movement thereof into batteryposition whereby said ring is initially deformed into obturating contactwith said beveled shoulder and with the interior surface of the barreland is thereafter additionally deformed during the firing of thecartridge to fully bridge the gap created between the bolt and thebarrel by the rearward setback imparted to the bolt upon firing.

2. The cartridge defined in claim 1 wherein said case is fabricated ofaluminum and said obturating ring is fabricated of brass.

3. The cartridge defined in claim 1 including means responsive to theforces generated during the firing of the cartridge for locking saidobturating ring to said cylindrical portion of said case to permit thesubsequent extraction thereof from the firing chamber during movement ofthe bolt out of battery position.

4. In a firearm having a barrel and a bolt arranged for reciprocalmovement into and out of battery position relative to the barrel, thebolt having cylindrical recess in the front end thereof cooperating withthe breech end of the barrel to form a split firing chamber for acartridge provided with a rearwardly facing beveled shoulder and acylindrical primer housing of reduced diameter projecting centrallyrearward of the beveled shoulder, the improvement of means forobturating the gap produced between the bolt and the barrel by thesetback forces encountered during the firing of the cartridge, saidmeans comprising,

an obturating ring of a more deformable material than the cartridgeseated on the primer housing to extend rearwardly beyond the rear endthereof and forwardly beyond the split between the bolt and the barrel,

a beveled surface on the front face of said ring concentric with saidbeveled shouider of the cartridge and sloped to form a triangular spacetherebetween whereby the forward movement of the bolt into batteryposition deforms said ring into obturating contact with the beveledshoulder of the cartridge and with the interior wall surface of thebarrel and whereby the subsequent firing of the cartridge additionallydeforms said ring into obturating contact with the interior surface ofthe cylindrical recess in the front end of the bolt rearwardly of thesplit in the firing chamber, and

means responsive to the forces generated during the firing of thecartridge for locking said obturating ring to the cylindrical primerhousing to permit the subsequent extraction of the cartridge from thefiring chamber during the rearward movement of the bolt out of batteryposition.

2. The cartridge defined in claim 1 wherein said case is fabricated ofaluminum and said obturating ring is fabricated of brass.
 3. Thecartridge defined in claim 1 including means responsive to the forcesgenerated during the firing of the cartridge for locking said obturatingring to said cylindrical portion of said case to permit the subsequentextraction thereof from the firing chamber during movement of the boltout of battery position.
 4. In a firearm having a barrel and a boltarranged for reciprocal movement into and out of battery positionrelative to the barrel, the bolt having cylindrical recess in the frontend thereof cooperating with the breech end of the barrel to form asplit firing chamber for a cartridge provided with a rearwardly facingbeveled shoulder and a cylindrical primer housing of reduced diameterprojecting centrally rearward of the beveled shoulder, the improvementof means for obturating the gap produced between the bolt and the barrelby the setback forces encountered during the firing of the cartridge,said means comprising, an obturating ring of a more deformable materialThan the cartridge seated on the primer housing to extend rearwardlybeyond the rear end thereof and forwardly beyond the split between thebolt and the barrel, a beveled surface on the front face of said ringconcentric with said beveled shoulder of the cartridge and sloped toform a triangular space therebetween whereby the forward movement of thebolt into battery position deforms said ring into obturating contactwith the beveled shoulder of the cartridge and with the interior wallsurface of the barrel and whereby the subsequent firing of the cartridgeadditionally deforms said ring into obturating contact with the interiorsurface of the cylindrical recess in the front end of the boltrearwardly of the split in the firing chamber, and means responsive tothe forces generated during the firing of the cartridge for locking saidobturating ring to the cylindrical primer housing to permit thesubsequent extraction of the cartridge from the firing chamber duringthe rearward movement of the bolt out of battery position.